Interjection in English Grammar

What is Interjection?

Interjections are used to express emotion or to catch attention. These are rarely used in formal or business writing but commonly appears in advertising and promotional material, fiction, informal writ-
ing, and personal letters.
These are some of the most commonly used interjections:

never
great
help
ah
alas
my goodness
congratulations
good grief
hurry
no way
oh
ouch
outstanding
ugh
Wow